Sound devices are included in the different types of protection devices that can be used to remotely control an isolated individual or to disperse and disorganize a potentially dangerous group. These devices, called non-lethal sound (NLS) weapons, have many advantages in terms of their efficiency and relative harmlessness. These advantages include particularly:                Some limitation to the range related to attenuation of sound waves in free space, which can delimit the action zone of such devices. The amplitude of sound waves decreases in a known manner in proportion to the inverse of the square of the distance traveled by the wave.        The possibility of using low or very low frequencies of the order of a few tens of Hz to about a hundred Hz. In particular, these audible frequencies have a mechanical effect on the human internal ear. These effects usually cause nausea in man or even losses of equilibrium and thus prevent forward movement.        The lack of persistent physiological effects in the long term for an emitted sound level not exceeding a certain threshold, the annoyance caused to individuals suffering from the acoustic wave disappearing as soon as the emission stops.        
These advantages of control and reversibility of effects advantageously distinguish NLS from other types of mechanical and electromechanical devices that can also be used in similar circumstances.
On the other hand, existing sound protection devices have some well known disadvantages, particularly related to the low frequencies used.
A first disadvantage is in the difficulties that arise when it is required to generate very strong sound levels, of the order of 130 dB necessary to make the device efficient. This operation usually requires the use of large volume and heavy equipments, for example such as enormous loudspeaker enclosures, for which fast deployment and installation cannot be expected.
A second disadvantage is due to the lack of directivity of acoustic protection devices using compact equipment forming a unique acoustic source. For such sources, the insonification diagram covers a wide zone and in particular can include the area in which the user of the system is located. This disadvantage makes it difficult to control collateral effects.
A third disadvantage is also worth mentioning, due to the logistics, transport and implementation disadvantages of existing devices. This disadvantage is particularly severe in the case of systems using pneumatic or thermal energy sources, for example based on combustible gases, such as sources using quarter wave resonator tubes.